This application is the national phase under 35 U.S.C. xc2xa7371 of PCT International Application No. PCT/EP00/08330 which has an International filing date of Aug. 26, 2000, which designated the United States of America.
The invention relates to a vehicle tyre comprising a carcass ply extending between two bead regions, a tread region disposed between side walls and having a tread surface curved in the axial direction and a breaker reinforcing the tread region and arranged between the carcass ply and the tread region.
A vehicle tyre of this kind is known from DE 694 03 616 T2, in which the outer tread surface has a curvature which has a continually reducing radius from a point P located at a distance SP in the axial direction from the centre line of the tyre periphery which is equal to 20% of the distance from the tread centre to the neighbouring tread contact edge when the tyre is mounted on a tyre rim and normally pumped up. The contour of the breaker provided in this tyre follows the contour of the tread surface. Such a tyre however is not optimised and has problems in providing all the necessary properties at the same time.
It is the object of the present invention to provide a vehicle tyre which meets the demands made on a tyre ideally, in particular as regards weight, handling, safety, rolling resistance, comfort and the like.
This object is essentially satisfied in accordance with the invention, with a tyre mounted on a tyre rim and normally inflated, by the vertical spacing of the tread surface with respect to the breaker continually reducing, starting from the region of the tyre centre, towards the breaker edges and by the side walls being made at least essentially self-supporting.
It is in particular the spacing between the tread surface and the essentially flat or plane breaker, which is pre-set within the context of the teaching of the present invention, which allows the tyre to have an optimum shape. In particular, a comparatively narrow ground contact region can be realised, with a favourable change in the contact patch resulting during cornering, less heat being generated in the region of the belt edges as the belt edge is essentially only under strain during cornering, and with the shape and position of the breaker leading to good handling.
The side walls of the tyre are stiffened with reinforcing plies in such a way that the tyre becomes self-supporting. The shape and position of the reinforcements disposed within the carcass ply are selected so that, together with the bead core apex fully enclosed by the carcass ply, they form a stable assembly which acquires its required flexibility predominantly from the radially outer third of its height curved towards the tyre centre.